1. Field of the Invention
The present invention relates to a film clamp for use in apparatus such as a film scanner, and more particularly, to a film clamp for holding a film extremely flat in a film gate in such apparatus.
2. Description of the Prior Art
In various types of imaging apparatus, a photographic film must be clamped in a work station while a particular operation is performed on the film. In certain types of apparatus, for example, film scanners, the film must be held extremely flat in order for an image on the film to be recorded properly. One problem in maintaining the film flat is that photographic film has a natural curl due to an emulsion coated on one side of the film.
In a conventional film clamp, as illustrated in FIGS. 1 and 2, a film 1 is clamped against a platen 3 on all four sides of a rectangular aperture 5 by a vertical force represented by arrows 7. In the use of such a film clamp, the natural curl in the film 1 will be retained, and the film will not be held flat. Further, when all sides of the film 1 are clamped, any thermal variation of the film that occurs while the film is clamped can cause the film to buckle.
A further problem in known film clamps for film scanners is that it is difficult to advance short strips of film in the film gate relative to a scan beam of light. Normally, the film advance mechanism is located outside of the film clamp, for example, rollers operating on the film at opposite sides of the film clamp, and thus, the minimum length of film which can be handled is controlled by the distance between the rollers.